1. (Field of the Invention)
The present invention generally relates to a telephone system and, more particularly, to a telephone call selector for protecting a telephone subscriber from prank calls and wrong numbers.
2. (Description of the Prior Art)
As a matter of practice, a telephone subscriber can recognize that a telephone call is made to him or her, when he or she listens to a ringing sound generated from his or her telephone as a result of the arrival of a ringing signal from the calling party's telephone through a telephone line. Once the telephone rings, the receiving party is generally forced to answer the telephone and this is true even where a prank call or a wrong number has been made. Prank calls and wrong numbers are not really welcome and the receiving party is unable to ascertain whether or not it is a prank call or a wrong number before the telephone handset is unhooked.
In order to substantially avoid the prank calls and the wrong numbers, a telephone system has been suggested in, for example, the Japanese Laid-open Patent Publication No. 55-11668, published in 1980, wherein a telephone can ring only when dialed by those who are informed of an identifier code unique to such telephone. The identifier code can be arbitrarily chosen by the owner of a telephone when it is to be latched in his or her telephone.
According to this prior art telephone system, the owner of a particular telephone in which the identifier code has been latched must disclose his or her identifier code to those who are acquainted, familiar and/or associated in any manner with him or her. This is possible so long as the owner remembers his or her identifier code, and once he or she forgets it, a problem would arise.
Apart from the problems associated with the prank calls and the wrong numbers, the sequential dialing of the station number and the subscriber's number often irritates the calling party who is then dialing because of a substantial time required to have his or her telephone connected with the receiving party. In view of this, a telephone having an automatic dialing device built therein is currently widely used in practice such as disclosed in, for example, the Japanese Patent Publication No. 53-30601 published in 1978. According to this publication, the automatic dialing device includes a memory means for storing at respective address locations a plurality of telephone numbers of those who are acquainted, familiar and/or associated in any manner with the calling party, so that, either by pushing one of push buttons associated with the respective address locations or by dialing one of address numbers allocated to the respective address locations, each of which address numbers consisting of a smaller number of digits, for example, two or three digits, than the number of digits comprising a telephone number, the telephone of the calling party can be connected with that of the receiving party.